package ExerChapter13Wrapper;

public class String_ {
    public static void main(String[] args) {
        String str = null;
        StringBuffer foo = new StringBuffer();
        // 实际是插入“null”
        // foo.append(str);
        // 这样会报错，因为源码有个int length = str.length();但是str为空；
        StringBuffer foo1 = new StringBuffer(str);        
        System.out.println(foo.length());
        System.out.println(foo.toString());
        
    }
}
